1. Field of the Invention
This invention relates to a low-noise transformer, and more particularly to an improvement for reducing noise originating from an output transformer of an inverter.
2. Description of the Prior Art
A known output transformer of an inverter, as exemplified in a book, "Design and Manufacture of Transformers" supervised by Hisao Kimura, pp. 182-185, Denki Shoin, Japan, is shown in FIG. 1 in which reference numerals 1 and 2 designate primary and secondary windings, respectively, of the transformer 5; 3, spacers arranged circumferentially and between the primary and secondary windings 1, 2 for fixedly-supporting them; and 4, an iron core of the transformer 5.
FIG. 2 illustrates the circuitry of the transformer 5 shown in FIG. 1, and FIG. 3 is a circuit diagram illustrating the interconnection between the transformer 5 and an inverter. In FIG. 3, reference numerals 10 and 11 indicate an inverter connected to the primary winding of the transformer 5 and a load connected to the secondary winding, respectively.
The description of the action of the conventional transformer for use as an output transformer of an inverter is given below:
Referring to FIG. 3, assuming that an alternating current voltage E.sub.1 (t) is applied to the primary winding 1, then in the ideal case the magnetic flux, denoted by .phi., is expressed as ##EQU1## where n.sub.1 is the numbers of turns for the primary winding.
If all the magnetic flux .phi. intersects with the secondary winding, then the voltage E.sub.2 established at secondary winding 2 is given by ##EQU2## where n.sub.2 is the number of turns for the secondary winding.
The output voltage of the inverter 10 includes many harmonic voltage components in respect to the fundamental frequency voltage. In this state, the harmonic voltage components induce electric current in the primary and secondary windings when the interconnection between transformer 5 and load 11 is completed.
The above-described prior art transformer for use as an output transformer of inverter, having the construction shown in FIG. 1, is disadvantageous in that it can not operate without considerable noise due to harmonic voltage component of the inverter.